preinvasive lesions of the lung

Lung cancer is now the leading cause of death from cancer in Australia. Most patients are diagnosed with late-stage disease.

Although diagnosis at pre-invasive stages could theoretically improve outcomes, mooted precursor lesions are often asymptomatic and often undetectable by non-invasive investigations.

Nonetheless, they merit study to identify early and essential molecular steps involved in lung carcinoma pathogenesis, with the aim of developing therapies targeted against one or more such steps.

Some lung cancers appear to develop via a series of progressive morphological changes with correlating molecular alterations, but others seem to arise in histologically normal epithelium, and these differences may reflect anatomically and functionally distinct epithelial compartments of the respiratory tract.

Other lesions that likely represent pre-invasive lesions, but which are not currently WHO-listed, include: human papillomavirus (HPV)-related respiratory papillomatosis mesothelioma in situ.

No single cancer stem cell marker has been identified.

Field cancerisation plays an important role in lung cancer development, and includes the spread of pre-invasive clones along the respiratory epithelium or the occurrence of multiple separate foci of pre-invasive abnormalities such as squamous dysplasia and carcinoma in situ.

In addition to well-characterised step-wise progression in squamous cell carcinomas and some adenocarcinomas, alternative pathways exist, and are currently being investigated.

Molecular techniques, including miRNA screening on blood samples or cytology samples-such as sputum samples-may become clinically relevant and more accurate in predicting lung cancer progression.